The invention relates to a fluid control element.
U.S. Pat. No. 4,765,370 shows a fluid control element comprising a housing in which two control chambers are formed, which are each isolated from each other and comprise a working port each as well as two pressure ports, two of the ports being provided with a sealing seat each. The fluid control element further comprises a switching element movably mounted in the housing and comprising a sealing part in each control chamber, the sealing part cooperating with the sealing seats such that these are opened or closed, and still further comprises an actuating member for the switching element. This fluid control element represents a 4/2-way valve for actuating hydraulic actuator cylinders, for example. When actuating, for example, a double-acting hydraulic cylinder, the working port of the one control chamber is connected to a working port of the hydraulic cylinder and the working port of the other control chamber is connected to the other working chamber of the hydraulic cylinder. In a first position of the switching element, the resting position, the one working chamber of the hydraulic cylinder is pressurized so that a movement occurs in a first direction, whilst in an activated position of the switching element into which the switching element is moved by an electric magnet, the other working chamber of the hydraulic piston is pressurized so that a movement occurs in the opposite direction.
It is often required, however, in addition to a movement of the hydraulic piston in a first and a second direction that the hydraulic piston, for example, is maintained fixed in a position or is freely movable. For this purpose 4/3-way valves are needed as described with reference to FIG. 13. Illustrated schematically in FIG. 13 is a hydraulic piston 1 disposed between two working chambers 2, 3. The working chamber 2 is connected to a working port A of a 4/3-way control element illustrated schematically and identified by reference numeral 10, and the working chamber 3 is connected to a working port B. Furthermore, two pressure ports P, R are provided, port P providing a pressurized fluid and port R forming a return flow conduit.
The control element shown as example 1 permits three operating conditions. In the left-hand switching position the hydraulic piston 1 is biased so as to move to the right. In the middle switching position the hydraulic piston 1 is blocked. In the left-hand switching position the hydraulic piston 1 is biased so as to move to the left.
The examples 2 and 3 likewise make possible three switching positions, the left-hand and the right-hand switching positions in each case corresponding to the right-hand and left-hand switching positions of the first example. The middle switching position in example 2 results in the hydraulic piston 1 being freely movable and the middle switching position of example 3 results in the hydraulic piston 1 being blocked by the pressure furnished by the pressure port P.
Hitherto, achieving such switching functions necessitated the use of piloted slide valves.
The object of the invention consists in providing a simple, direct-acting control element having a 4/3 operational mode to thus reduce the expense in terms of technical equipment in actuating a cylinder and to permit a more direct and faster operation of actuator cylinders and actuators, respectively.
To achieve this object, a fluid control element is provided which comprises a housing in which two control chambers are formed, which are isolated from each other and comprise a working port each as well as two pressure ports. Two of these ports are provided with a sealing seat each. The fluid control element further comprises a switching element movably mounted in the housing and comprising a sealing part in each control chamber. The sealing part cooperates with the sealing seats such that these are opened or closed. The fluid control element further comprises an actuating member for the switching element, the actuating member being able to bring the switching element into three positions. In this way the desired three switching positions are achievable with a control element having two control chambers without additional slide valves being necessary. Such an actuating member with which the switching element is may be brought into three positions is, for example, a solenoid drive having a polarized drive element, the permanent magnet of which in the non-energized condition of its solenoid holds the switching element in a middle position, which also represents the resting position, and in the energized condition shifts the switching element into the one or the other direction depending on the direction of current flow.
In accordance with one preferred embodiment of the invention it is provided for that the sealing seats of one control chamber are disposed opposite each other on the one and the other side of the control chamber and that the sealing part arranged in this control chamber is configured with two opposing tongues disposed between the sealing seats and configured so as to be elastically resilient, and in the resting position are spaced away from each other such that they may simultaneously close the two sealing seats. In this embodiment all ports in the middle or resting position are closed. By moving the switching element, starting from the resting position, into the one or the other direction the desired ports may be selectively opened.
As an alternative it may be provided for that the sealing seats of one control chamber are disposed opposite each other on the one and the other side of the control chamber and the sealing part arranged in this control chamber is in contact with either the one or the other sealing seat. In this embodiment one sealing seat of each control chamber is closed in the resting position. As soon as the switching element is actuated in any direction, one of the sealing parts is lifted from the corresponding sealing seat and pressed against the opposite sealing seat whilst the other sealing part remains in contact at the corresponding sealing seat with no change in the switching condition in this control chamber. Depending on how the various ports are put in circuit, a variety of different switching conditions results.
In this alternative the sealing parts arranged in the two control chambers extend in the same plane or in different planes. In the resting position one of the sealing parts is then in contact with the sealing seat disposed on one side of the corresponding control chamber whilst the other sealing part is in contact with the other sealing seat arranged at the other side of the other control chamber. When the sealing parts are arranged in the same plane, the actuating travel needed for making the changeover is achieved by differing the spacing of the sealing seats away from the plane of the sealing parts in the resting position, whereas when the sealing parts are arranged in different planes the necessary actuating travel is achieved by different spacings assumed by the sealing seat from the sealing parts being in the resting position.
In accordance with a further embodiment it may be provided for that the sealing seats of one control chamber are arranged mutually staggered on the one and on the other side of the control chamber, and that the sealing part arranged in this control chamber is configured with two tongues arranged side by side, each of which being assigned to one of the sealing seats and configured so as to be springy and elastic. The effect of this configuration is basically the same as that described above having the two tongues opposite each other, except that here a larger number of switching conditions is possible. If required, in one of the control chambers the configuration as described above including opposite sealing seats and opposite tongues may be provided, whilst in the other control chamber the configuration having staggered sealing seats and tongues lying side by side may be employed.
It is preferably provided for, however, that in both control chambers the sealing seats of one control chamber are arranged mutually staggered on the one and the other side of the corresponding control chamber, a maximum number of switching conditions being possible in this case.
In this embodiment it may be either provided for that the tongues of the sealing parts of the switching element arranged in the two control chambers extend in the same plane. Technically the same effect is achievable by providing the two tongues, arranged in one chamber, so as to be mutually staggered. In cooperation with a suitable arrangement of the sealing seats relative to the arrangement of the tongues in the resting position, a variety of conditions is possible, i.e. the sealing seats in the two control chambers either being arranged such that in the resting position the tongues of the sealing parts are in contact with all sealing seats in the two control chambers, or as an alternative the sealing seats in the two control chambers are arranged such that in the resting position the tongues of the sealing parts are in contact with all sealing seats of a sole control chamber and with no sealing seat of the other control chamber. Finally, it is possible that the sealing seats are arranged in the two control chambers such that in the resting position the tongues of the sealing parts are each in contact with one sealing seat in each control chamber. Depending on the configuration selected in each case a wealth of different switching conditions is achieved with which any desired mode of actuating an actuator, for example a hydraulic actuating cylinder, is achievable.
Advantageous aspects of the invention read from the sub-claims.